WASHINGTON — The Soviet Union is developing its own brand of "Star Wars" missile defense and seeks to halt U.S. research into laser weaponry because it wants a monopoly on the system, Defense Secretary Caspar W. Weinberger said today.

Weinberger unveiled the Pentagon's fourth edition of "Soviet Military Power" that said the Soviets could deploy a ground-based laser weapon by the early to mid-1990s.

"They already have ground-based lasers that could be used to interfere with U.S. satellites," the publication said. It said the Soviets generally have made technological advances in all phases of weapons production, including a new fighter and helicopter that are similar in appearance to U.S. models.

Bound in Red

Weinberger produced the booklet, covered in red, at a news conference transmitted live via satellite to reporters in Brussels, Bonn and Tokyo.

The "most important" disclosures in the publication, he said, concern the "Soviet Union's high-energy laser program. The importance of it is they've passed beyond research and are developing prototypes.

"All of this emphasizes the very extensive work on defensive systems. These are systems that the Soviets are attempting to keep the Americans from achieving. They apparently want a monopoly in this. They are doing it themselves and they want to be left alone to do it."

Moscow has sought to put the U.S. Strategic Defense Initiative, or "Star Wars" project, on the bargaining table at the arms control talks in Geneva. But the Reagan Administration has said it will not negotiate on that project.

Cites 'Differences'

Weinberger said it would be destabilizing for the Soviets to be the first to deploy a "Star Wars" defense, although the Administration has maintained that such a defensive system would contribute to stability because it would make nuclear weapons "impotent and obsolete."

Asked why the Soviets should not be first, Weinberger said it was because of the "differences in the systems" of the United States and the Soviet Union and because of "the ways they have behaved in the past."

New disclosures about Soviet advances in "Star Wars" technology marked the major difference between the book's latest edition and its predecessors, possibly as part of the Administration's campaign for its own "Star Wars" efforts, for which it wants $3.7 billion next year.

"The U.S.S.R.'s high-energy laser program, which dates from the mid-1960s, is much larger than the U.S. effort," the book said. "They have built over a half-dozen major research and development facilities and test ranges and they have over 10,000 scientists and engineers associated with laser development."

'80s Prototypes

The book said Soviet experimentation in such technology could lead to prototypes for ground-based anti-missile lasers by the late 1980s, testing for components of "a large-scale deployment system" in the early 1990s and a prototype of a space-based particle beam system ready for testing in the late 1990s.

Although large-scale deployment "is not likely this century" because of the "many difficulties in fielding an operational system," the book said, "with high priority and some significant risk of failure, the Soviets could skip some testing steps and be ready to deploy a ground-based (anti-missile) laser by the early to mid-1990s."

That is about comparable to the timetable set up for the U.S. Strategic Defense Initiative.